elapid said:
Two things. Firstly, cyclists are not riding at these altitudes so this study has no relevance to performance enhancement from sea level to the type of altitudes typically experienced in the Alps or the Pyrenees. For instance, the Col du Galibier is often the highest pass in the TdF. At 2645 m or 8678 ft, the Galibier is approximately half the altitude where dexamethasone has a positive effect on performance in the mountaineering study you cited.
Secondly, the term steroids can be confusing. Dexamethasone is a glucocorticoid and is used for its antiinflammatory and immunosuppressive effects. Dexamethasone and other glucocorticoids such as hydrocortisone have no performance enhancing effect, at least at the altitudes below 15000 ft.

Glucocorticoids are very different to the "steroids" used for performance enhancing in athletes. The performance-enhancing steroids are anabolic steroids and these are related to male hormones, not glucocorticoids. Anabolic steroids are performance enhancing because they improve muscle strength and recovery, thus allowing users to trainer harder and longer.
i know the difference. point is what is the difference at lower altitudes?
.Take Dex and Climb Better at High Altitude
Friday August 14, 2009
High altitude mountaineers have long taken dexamathasone or dex for treating altitude-related illnesses like high altitude pulmonary edema (HAPE) and acute mountain sickness (AMS). Now a Swiss study reveals that taking dex can dramatically improve exercise capacity and performance at high altitude.
The study, published in the August 15th issue of the American Journal of Respiratory and Critical Care Medicine by the American Thoracic Society, used 23 mountaineers with a history of HAPE. The climbers were randomly given tadalifil, dexamethasone, or a placebo the day before a cable car ascent from 3,609 feet at Alagna, Italy to 10,499 feet, where they climbed to 11,975 feet and spent the night. The next day the climbers ascended to Capanna Regina Margherita at 14,957 feet. Exercise tests and echocardiographic exams were conducted on the summit.
“Reduced oxygen content in the air is the major limiting factor at high altitude.
Reduction in exercise capacity goes in parallel to the reduction in oxygen up to an altitude of approximately 4,000 meters. At higher altitudes, there is an even further reduction in exercise capacity,” says Dr. Manual Fischler, one of the lead researchers. “As expected, exercise capacity at high altitudes was diminished among all groups and key indicators of cardiopulmonary stress were elevated.”
Subjects who took tadalafil and dexamethasone fared better in oxygen use than the placeo group, but the dex group had two major advantages. First, the heart rate of the dex group increased but less than the other groups. Second and more significantly, the VO2max, a measurement of how efficiently the body uses oxygen, was much higher in the dex group at high altitude. The study found that elevated blood pressure in the lungs decreases the body’s ability to use oxygen during exercise. Dr. Fischler says, “Our study indicates that for HAPE-susceptible climbers, taking dexamethasone improved exercise capacity, oxygen uptake kinetics and decreased the anaerobic threshold.”
What that all means is that climbers who took dex felt better at altitude, climbed better, and had “fewer altitude-related discomforts” than the other two groups.
note the bold. it doesn't say that it does nothing below 15000 ft.
and again, i'm not saying that it's a super drug like epo, but aspart of a regimen would be really helpful.
one of the best effects i had was zero muscle soreness, no matter what i did. in some ways it was like being 18 again.